Methods are now worked out for separation of some of the native mycobacterial antigens present in culture filtrate of M. tuberculosis. Applied to a briefly heated, concentrated filtrate, the technique has allowed isolation of two of the most important antigens. Three of the antigens will be isolated in useful quantity from unheated filtrate and characterized. Specific precipitating rabbit antisera have been prepared against one of these antigens; production of antiserum will be undertaken for the other two antigens. The ultimate goal is to study individual antigens in Type IV mycobacterial hypersensitivity. Anti-dinitrophenyl antibody produced upon immunization of normal guinea pigs and animals rendered specifically unresponsive to acquiring contact-type (Type IV) hypersensitivity to dinitrochlorobenzene will be studied comparatively by isoelectric focusing versus labeled dinitrophenyl hapten.